Zimmer purchased his new pets from scientists at the University of Kentucky, who modified the genetic makeup of the axolotls with Green Fluorescent Protein (GFP), the protein responsible for making jellyfish and other organisms glow naturally. The process doesn´t hurt, and Zimmer says it´s unlikely that the glowing axolotls know they are any different from their brothers and sisters found in their natural habitat in Mexico.

Zimmer uses them to help explain the importance of GFP research. The protein allows scientists to see things that couldn't otherwise be seen, even with a microscope. For example, cancerous molecules can be tagged with GFP, and researchers can actually watch as the molecules spread to other parts of the body.

Zimmer has also discovered that GFP works wonders in elementary, middle and high school classrooms. "I want to get young people excited about science," Zimmer said. "And they love to see the animals glow."